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Thread: fluorescence

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    Default fluorescence

    I'm interested in an arts project that would involve fluorescent compounds that become active within a narrowly banded grouping, say 310 nm, 330 nm and 350 nm. The idea would be to use a tunable laser or LED source (if there is such a beast) to edge-light the compounds in a materials envelope (glass and plastic stop UVC, eg, and a quartz envelope would have to be used if I wanted compounds that fluoresce on exposure to those wavelengths). I'm wondering what the price range for tunable lasers, specifically in the UV band, are and whether or not they are competitive with tunable UV LED sources.

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    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Tunable UV lasers start in the 100,000$ range
    Your looking at a optically pumped oscillator and a pump laser and a frequency tripler to get to UV. All expensive solid state hardware.
    The argon ion UV laser is a possibilty, but its two major UV lines are at 325 and 365, not quite far enough apart to do what you wish without some very specialized phosphors. A UV argon costs about 45,000 new and maybe 15-17K$ for a used and rebuilt model 171 with UV optics. Since the UV lines are AR III ion instead of ARII for visible they are horribly inefficient. I know, I maintain one for a university.

    tunable LEDs are just a laboratory curiousity now. I suggest you look at at arc lamps and flashlamps for your project, they are easily filtered. A UV dmd mirror kit with a arc lamp (say a cermax,tm perkin elmer) is much more viable concept and much cheaper then a UV laser. The quartz flashlamps are cheap, but avoid laser pumping lamps on ebay, because they often have cerium doped quartz to block the UV emission using downconversion. With small lamps you can get a fast enough rep rate to appear CW. Cermax lamps show up on ebay cheap as medical endoscope illuminators, I just scored a 300 watt one for 40$ in working order, usually theu go around 400$. The lamp however has its short UV filtered out as it blackens the fiber optics. PE gets 500-700$ for a lamp without the UV filter to get the short wavelengths.

    The UV leds I've seen show up at 350,325, and 410 or so. At about 3$ a uv led for maybe 10 mW output. Mercury filled flourescent lamps for germacidial work give you short UV as well and fit standard fixtures. BLB or blacklight blue tubes give you the UV A. If you keep the cathodes hot, flourescent lamps can start and stop very quickly. Dichroic filters for UV show up on ebay by a seller named BJOMEJAG, and you can angle tune them, IE a very broad dichroic (20-30 nM) will change transmission as the cosine of teh angle as you rotate it.
    Please remember, all this UV is a serious eye hazard, conjuntivitus hurts! Permanent corneal damage will occur over time, although lexan polycarbonate sheets make good UV blockers for 350-370. We dont buy safety goggles for our UV lasers at work, the standard polycarb goggles work just fine at short wavelengths.

    UV lasers have been used for shows before, but not in wavelength selective mode. Once upon a time I made a screen using a UV hecad and a photosenisitive material that changed from white to blue under UV. The idea was to make a daylight laser show. Worked great except A little problem popped up called the Sun.
    Not to mention the persistance time of the material was on the order of 30 seconds. So much for motion graphics.

    So you have a good idea, but laser technology just isnt there yet. try good old arc sources.

    Steve Roberts
    Last edited by mixedgas; 05-29-2007 at 06:59.

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